China poised to overtake US as world's largest economy, research shows

Economists previously expected the US – number 1 since the 19th century – to keep the top spot until 2019

The container area at the Yangshan Deep Water Port, part of the Shanghai Free Trade Zone: research shows China will overtake the US this year as the world's largest economy. Photograph: Carlos Barria/Reuters

Using this measure, the ICP concluded that the size of the Chinese economy in 2011 was 87% of the US economy, up from 43% in 2005 when the last comparison was made.

"The United States remained the world's largest economy, but it was closely followed by China when measured using purchasing power parity," the ICP said in its report.

According to expectations from the International Monetary Fund for growth between 2011 and 2014, that would put China ahead of the US this year.

The US has been the world's largest economy since the late 19th century, and economists previously thought it would not be knocked off the top spot until 2019.

America's share of world GDP was 17.1% in 2011, according to the ICP, using the purchasing power measure. China's share was 14.9%. India overtook Japan to become the world's third largest economy with 6.4% of GDP.

On the same measure the UK was ranked the ninth largest economy, with 2.4% of global GDP.

The report found that although high income countries account for half of the world's GDP, they are home to only about 17% of the world's population.